1. Field of the Invention
The present invention relates generally to a filtering material employable in various kinds of application fields in the form of a sanitary filter, a deodorizing filter incorporated in various kinds of deodoring units, foodstuff packing materials having a capability of sterilizing and deodorizing or the like. More particularly, the present invention relates to a filtering material which can effectively and reliably adsorb very fine infectious or antigenous particles such as viruses, bacteria or the like. Further, the present invention relates to a method of producing a filtering material of the foregoing type.
2. Description of the Prior Art
The applicant common to the present invention has already made proposals with respect to a method of producing a novel filtering material for capturing very fine foreign material such as virus or the like in Japanese Patent Applications Nos. 278487/1990, 29301/1991 and 163903/1991.
For example, each of the proposed methods is practiced by way of the steps of preparing an aqueous treatment solution by dispersively dissolving a predetermined quantity of porous apatite particles and a predetermined quantity of a water soluble glucan in water, dipping a sheet-shaped raw material in the aqueous treatment solution or spraying the latter over a sheet-shaped raw material or bringing a rotating roller wetted with the aqueous treatment solution in contact with a sheet-shaped raw material, and drying the sheet-shaped raw material coated with the aqueous treatment solution while the porous apatite particles are included in the sheet-shaped raw material with the aid of the water soluble glucan serving as a binder.
In addition, a method of the foregoing type proposed by the applicant is practiced by way of the steps of preparing an aqueous preliminary treatment solution by dissolving only a water soluble glucan in water to prepare an aqueous preliminary treatment solution, allowing the preliminary treatment solution to adhere to a sheet-shaped raw material, thereafter, allowing porous apatite particles to adhere to the sheet-shaped raw material coated with the aqueous preliminary treatment solution before the preliminary treatment solution is completely dried, and finally, drying the sheet-shaped raw material including the porous apatite particles with the aid of the water soluble glucan serving as a binder.
A characterizing feature of any one of the conventional methods of the foregoing type each proposed by the applicant consists in that porous apatite particles composed of a kind of calcium phosphate particles are bonded to a sheet-shaped raw material with the aid of water soluble glucan serving as a binder.
In contrast with a conventional filtering material, a filtering material produced by employing each of the conventional methods proposed by the applicant exhibits excellent properties of adsorbing and filtering very fine infectious or antigeneous foreign materials such as viruses, pollen, or the like, unattainable with conventional filtering materials. In the circumstances as mentioned above, the filtering material produced by employing each of the aforementioned proposed conventional methods does not exhibit anything basically inconvenient for filter's users.
However, in addition to the necessity for adding a gas generating substance to the raw material for the purpose of imparting porosity to the apatite, and moreover, exactly controlling the steps of sintering and granulizing, it is required that the composition ratio of phosphor to calcium be strictly controlled. For this reason, there arises a slight inconvenience that it is considerably difficult to practically produce a filtering material.